In November-December 1995, the Interball TAIL spacecraft passed many times in nearly radial direction through the midtail and near-Earth plasma sheet near midnight. In some orbits the spacecraft skimmed close to the neutral sheet for many hours providing a survey of plasma sheet dynamics, most of these 'NS skimming' passes have been supported by extensive observations of substorm effects near the spacecraft footpoint in the Scandinavian sector Throughout this period the activity was generally low, but in most passes the distinct (although weak) substorm events have been recorded. We present first results of conjugate ground-spacecraft correlative studies during these passes to characterize the various activity observed (multiple impulsive substorm activations, pseudobreakups). Particularly, we emphasize that plasma sheet response to weak (<50 nT) substorm onsets (immediate dipolarization in the near tail and rapid plasma sheet thinning) is the same as for the strong substorm onsets, and argue that ionospheric feedback is not crucial to excite the breakup in the plasmasheet.